BzipValueTransformer

An NSValueTransformer that decompresses NSData into an NSString using my NSData+Bzip2 category (see NSDataPlusBzip). It is reversible. � BryanWoods

// Bzip2ValueTransformer.h @interface Bzip2ValueTransformer : NSValueTransformer

@end

// Bzip2ValueTransformer.m

1. import "Bzip2ValueTransformer.h"
2. import "NSData+Bzip2.h"

@implementation Bzip2ValueTransformer

+ (Class) transformedValueClass { return [[[NSString]] class]; }

+ (BOOL) allowsReverseTransformation { return YES; }

- (id) transformedValue:(id)data { // decompress return [[[[[NSString]] alloc] initWithData:[data bunzip2] encoding:NSUTF8StringEncoding] autorelease]; }

- (id) reverseTransformedValue:(id)string { // compress return [[string dataUsingEncoding:NSUTF8StringEncoding] bzip2]; }

@end

---

To give an idea of how it's used, my test project is just a Cocoa Document-based Application with an NSTextView bound (�la CocoaBindings) to an NSData in MyDocument. Selecting Bzip2ValueTransformer in the Bindings palette in Interface Builder handles all of the heavy lifting.

// MyDocument.h @interface MyDocument : NSDocument { NSData text; }

@end


// MyDocument.m

1. import "MyDocument.h"
2. import "Bzip2ValueTransformer.h"

@implementation MyDocument

+ (void) initialize { [[[NSValueTransformer]] setValueTransformer:[[Bzip2ValueTransformer new] autorelease] forName:@"Bzip2ValueTransformer"]; }

- (void) dealloc { [text release]; [super dealloc]; }

- (NSString ) windowNibName {

   return @"MyDocument";

}

- (NSData ) dataRepresentationOfType:(NSString )type { return text; }

- (BOOL) loadDataRepresentation:(NSData )data ofType:(NSString )type { text = [data retain]; return (text != nil); }

@end